In the structure of a wind turbine tower, suitable for the production of electric energy, a foundation capable of always firmly providing a correct and stable positioning of the tower with respect to the surrounding ground, though in presence of all possible stresses during use, is necessarily required.
Generally, these foundations for wind turbine towers require providing an excavation, providing a containment and reinforcement structure according to preset schemes and lastly casting considerable amounts of concrete to obtain imposing reinforced concrete structures. The foundation has a circular or generally polygonal structure, with the aim of optimising the response of the foundations in any direction of the wind. These shapes cause problems related to the formwork and the creation of the plinth suitable for such shape.
In any case, a lot of care and expertise is required to prepare the foundation complex capable of meeting both the law requirements and specific needs arising from the local conditions of use of the wind turbine tower.
Furthermore, it should be clear that such an important structure requires a considerable amount of time for preparation thereof. A further problematic element is that regarding the fact that such towers are not always prepared in positions easily accessible by the machines for transporting the concrete and hence even this gives rise to correlated problems.
The preparation of such foundations cannot be carried out under harsh weather conditions such as intense cold, rain, etc and additionally concrete seasoning times must be complied with before mounting the towers. Lastly, this method of preparation requires the presence of operators and manpower, over long periods of time, on the site where the wind turbine tower is intended to be constructed.
Document WO 2008/036934 describes a modular system of foundations for wind turbine towers in which only part of the foundation elements is prefabricated. Other elements, such as for example the entire base slab, instead require casting considerable volumes of concrete on site.
Documents WO 2005/012651, EP 1 262 614 and JP 2000/283019 describe concrete foundations for wind turbine towers made up of a single monolithic base, usually obtained by means of an on-site casting of concrete.